Synthesis of hexadiene dinitrile and product



Patented Oct; 18, 1949' SYNTHESIS OF nsxanm nmrrm v AND rnonnc'r Irving B. Webb, Brandywine Hundred, m, as-

v signor to Wilmingto No Drawing.

a 1 This invention relates to the synthesis of 1,6- dicyano-ZA-hexadlene and related compounds.

This invention is based upon the discovery that compounds of the formula.

CE=CHCROHCRDHCH=CH2 R being a member of the class consisting of hydrogen and methyl groups (and certain other radicals hereinafter disclosed), react with hydrogen cyanide in the presence of a soluble cuprous salt in an aqueous acidic medium, to form dinitriles of the formula,

Evidently two molecEIlia-r rearrangements (termed allylic rearrangem ts") occur simultaneously during the formation of the said nitriles, with the result that both of the nitrile groups in the product occupy terminal positions. These unsaturated nitrilesin which the nitrile groups are positioned terminally arebelieved to be novel compositions of matter.

The unsaturated glycols which are employed as reactants in the practice of the invention'lnay be prepared by any suitable means such as by reduction of alpha,beta-unsaturated carbonyl compounds with zinc amalgam in acetic acid. For example, 3,4-dihydroxy-L5-hexadiene can be prepared by reduction of acrolein, using the said zinc amalgam-acetic acid reducing agent. Similarly, 3,4-dimethyl-3A-dihydroxy-1,5-hexadiene can be prepared by reduction of methyl vinyl ketone; also, 3,4 diphenyl-3,4-dihydroxy-1,5- hexadiene can be obtained by reduction of phenyl vinyl ketone, and 2,5-dimethyl-3,4-dihydroxy- 1,5-hexadiene by reduction of methacrolein.

Any water-soluble cuprous salt may be employed as a catalyst the practice of. the invention. It is generally preferred to employ cuprous chloride, and to have ammonium chloride and copper powder present in the reaction mixture to keep the copper salt in the cuprous form. The temperature of the reaction mixture during the practice of the invention isgenerally below about 200 C. and is preferably within the range of 75 to 150 C. Any suitable reaction pressure may be employed, the preferred pressure being not substantially above the pressure required to keep the hydrogen, cyanide from escaping from the reaction mixture.

The invention is illustrated further by means of the following examples:

Example 1.A reaction mixture containing 50 grams of 3,4-dihydroxy-L5-hexadiene, B. P. 80

C./5 mm. (CHa=CHCHOI-ICHOHCH=CH2), 100' cc. HCN, 18 grams cuprous chloride, 6 grams am- E. I. du Pont de Nemonrs& Company,

a corporation ofDelawa-re nppuauon December 11, 1948, Serial No. 64.912

5 Claims. (0]. 260-4653) monium chloride, 1 gram copper powder, 15 cc. water and 1 cc. of concentrated hydrochloric acid was heated in a shaker tube for four hours at 100 C. The resulting product was extracted with chloroform and the chloroform in the extract was evaporated, whereby an oily residue was obtained. Upon crystallization of this residue from methanol a white crystalline product (10 grams, M. P. 89 C. to 92 C.), was obtained. This ma terial had the formula, CsHsN: (calc. N, 21.2,

C, 72.7, H, 6.1; found N, 20.65, C, 71.5, H, 6.3% This product had the structure as shown by hydrogenation to octamethylenediamine, NH2(CH2) aNm.

From the mother liquor was isolated by vacuum distillation a mixture (25 grams) of the intermediate cyanhydrin 1 cyano 4 hydroxy-2,5- hexadiene,

NEC--CH2CH=CH-CHOHCH=CH2 and the dinitrile. This mixture distilled at 124 to 128 C. at 1 mm. as a partially crystalline oil having the following analysis: N, 14,5%; OH no., 162 mg. KOH per gram. Calculated for cyanhydrin: N, 11,4%; OH no., 456 mg. KOH per gram. This cyanhydrin was recycled as follows: 25 grams of the cyanhydrin was heated for 4 hours at 100 C. with ml. HCN, 15 ml. H20, 2 ml. conc. HCl, 9 grams C112C12, 3 grams NHiCl, 1 gram Cu powder. The reaction product was extracted with chloroform- The solvent was evaporated and the dinitrile isolated by crystallization from methanol.

The 3,4-dihydroxy-1,5-hexadiene which was employed inthis example was prepared by the following method:

Two-hundred and forty grams of zinc metal After standing overnight, the reaction mixture 7 was filtered; the filtrate was saturated with salt and continuously extracted with etherfor 48 hours. The ether extract was treated with anhydrous potassium carbonate until all acetic acid and water were removed, and distilled. The yield of 3,4-dihydroxy-L5-hexadiene, boiling at C. at 5 mm. of Hg, was 117 grams (56%).

Example 2.-A mixture containing 45 grams 3,4-dihydroxy-L5-hexadiene, cc. HCN, 36

grams cuprous chloride, 12 grams ammonium chloride, 2 grams copper powder, 30 cc. water, and 2 cc. of concentrated hydrochloric acid was heated in a reaction vessel equipped with a stirrer gave 5 grams of CNCHzCH;CHCH=CHCH2pN, I

M. 9. 89 to 91 C.

It is to be understood that the foregoing examples are illustrative only and that numerous methods of practicing the invention will occur to those who are skilled in the art. Forexample, any suitable cuprous salt may be employed and any of the known methods for keeping the cuprous salt in solution in the lower state of valence may be-employed. It is not necessary to use cuprous halides, since other organic or inorganic salts of copper are equally effective, provided they are water-soluble. Similarly any suitable organic or inorganic acid may be employed to keep the reaction mixture acidic during the course of the reaction. Acids which may be employed include sulfuric acid, phosphoric acid, acetic acid, trichloracetic acid, etc. The hydrogen cyanide which is required as a reactant in practicing the invention is preferably introduced into the reaction mixture as such, although, if desired, it may be formed in situby introducing a metal cyanide such as sodium cyanide or potassium cyanide, with a substantially equivalent quantity of an inorganic acid such as hydrochloric acid. l I

I claim: 7

-1. A process for the preparation of 1,6-dicyano- 2,4-hexadiene which comprises reacting a glycol of. the formula CH2=CHCHOHCHOHCH=CH2 with hydrogen cyanide in an aqueous acidic solution containing a dissolved cuprous salt a catalyst, whereby a dinitrile of the formula CNCHzCH=CHCH=CHCHzCN- is produced,- and thereafter separating the said dinitrile from the resulting mixture.

2. A process for the preparation of 1,8-dlcyano- 2,4-hexadiene which comprisesreacting a glycol of the formula CH1=CHCH0HCHOHCH=CH with hydrogen cyanide in the liquid phase at a temperature not in excess of 200? C. in the presence of an aqueous acidic solution containing a dissolved cuprous salt as catalyst, whereby a dinitrile of the formula CNCHzCH=CHCH=CHCHzCN is produced, and thereafter separating the said dinitrile from the resulting mixture.

' 3. A process for the preparation of 1,6-dicyano- 2,4-hexadiene which comprises reacting a glycol of the formula CHr=CHCHOHCHOHCH=Cm with hydrogen cyanide in an aqueous acidic solution containing a dissolved cuprous salt as catalyst at a temperature within the range of to C. whereby a dinitrile of the formula CNCH2CH=CHCH=CHCHrCN is produced, and thereafter separating the said dinitrile from the resulting mixture.

5. 1,6-dicyano-2,4-hexadiene.

IRVING D. WEBB.

REFERENCES crrEn The following references are of record in the file of this patent:

Willstatter et al.: Beilstein, Handbuch der Org. Chem, 4th Ed., 2nd suppl., p. 677 (1942). 

